The important role of exhaust system setting for injection mold

1. The source of gas in the injection mold.
(1) Air in the gating system and mold cavity.
(2) Some raw materials contain water that has not been dried out, and they are vaporized into water vapor at high temperature.
(3) Due to the high temperature of the injection mold during injection molding, the gas generated by the decomposition of some unstable plastics.
(4) Gases generated by volatilization or chemical reaction of some additives in plastic raw materials.
2. Hazards of poor exhaust
Poor exhaust of injection mold will bring a series of hazards to the quality of plastic parts and many other aspects. The main performance is as follows:
(1) In the process of injection molding, the melt will replace the gas in the cavity. If the gas is not discharged in time, it will be difficult to fill the melt, resulting in insufficient injection volume and unable to fill the cavity.
(2) Unobstructed gas will form high pressure in the mold cavity and seep into the plastic under a certain degree of compression, resulting in air holes, cavities, loose tissue, craze and other quality defects.
(3) Because the gas is highly compressed, the temperature in the mold cavity rises sharply, which causes the decomposition and burning of the surrounding melt, and causes local carbonization and burning of the plastic parts. It mainly occurs at the confluence of the two melts, the corner and the gate flange.
(4) The gas is not discharged smoothly, which makes the melt speed entering each cavity different, so it is easy to form flow marks and fusion marks, and reduces the mechanical properties of the injection mold.
(5) Due to the obstruction of gas in the cavity, the filling speed will be reduced, the forming cycle will be affected, and the production efficiency will be reduced.